Method and apparatus for transmitting and receiving signals in multi-antenna communication system

ABSTRACT

A method for transmitting a signal in a multi-antenna system is provided. The method includes designating an analog beam to a plurality of generated modulation symbol sequences corresponding to a plurality of antenna ports, for each antenna port of the plurality, multiplexing signals, to which a beam is designated by the beam assignment, to a plurality of beam groups each having the same antenna beam combination, mapping beam group signals generated by the beam multiplexing, to at least one Orthogonal Frequency Division Multiplexing (OFDM) symbol and time and frequency resources, generating OFDM symbol signals corresponding to one or more antenna beams by OFDM-converting the beam group signals according to the resource mapping, converting the OFDM symbol signals into analog Radio Frequency (RF) signals, and transmitting the analog RF signals via a plurality of antenna elements by carrying the analog RF signals on associated antenna beams by analog beamforming.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 13/677,660, filed on Nov. 15, 2012, which claimed the benefit under35 U.S.C. §119(a) of a Korean patent application filed on Nov. 16, 2011in the Korean Intellectual Property Office and assigned Serial No.10-2011-0119445, the entire disclosure of which is hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to transmission/reception of signals in acommunication system. More particularly, the present invention relatesto a signal processing and transmission/reception method and apparatusfor supporting analog beamforming in a digital multi-antenna system.

2. Description of the Related Art

An enhanced wireless communication system, such as a 3rd GenerationPartnership Project Long-Term Evolution (3GPP LTE) system, employsdigital signal processing architecture that transmits and receivessignals using a plurality of antennas. In order to support a variety ofuse environments and conditions during the use of multiple antennas,such a wireless communication system designates or assigns transmissionsignals to virtual antennas called antenna ports by digital processing.The transmission signals are mapped to actual transmit antennas, andtransmitted via a Radio Frequency (RF) unit and an antenna unit afterbeing converted into analog signals. Commonly, a signal transferred toeach antenna is completely processed in the digital domain, and theprocessing in the digital domain may flexibly apply a variety ofmulti-antenna algorithms that support a plurality of codewords and aplurality of layers. However, the conventional wireless communicationsystem may not employ more antennas, since it employs only the digitalsignal processing method to use multiple antennas. Because the number ofavailable antennas is limited, the available antenna gain is alsolimited.

Analog beamforming technology used in a communication system thatsupports relatively static stations, as in the Institute of Electricaland Electronics Engineers (IEEE) 802.11ad standard, may support a verylarge number of antennas and control beams using phase shift values orswitches in an analog unit. The analog beamforming technology shifts aphase of one analog signal by means of an RF unit, and transmits thephase-shifted signals via N_(T) antennas. This analog beamforming (or RFbeamforming) may significantly increase the antenna gain with the use ofa very large number of antennas, but its performance may be limitedbecause its digital unit may not employ various digital antenna signalprocessing technologies, including digital beamforming. In addition, theanalog beamforming technology supports only Time Division Multiplexing(TDM), but does not support Frequency Division Multiplexing (FDM).

This conventional technology either employs multi-antenna technology bydigital signal processing, or performs analog beamforming by controllingan analog unit. Therefore, it is unable to obtain the benefits of thetwo different technologies. Therefore, a new technology is needed toefficiently support both the multi-antenna technology by digital signalprocessing and the analog beamforming.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide a signal processing method and apparatus forefficiently supporting both multi-antenna technology by digital signalprocessing and analog beamforming.

Another aspect of the present invention is to provide a signalprocessing method and apparatus for flexibly coping with a variety ofuser and channel environments using a variety of digital multi-antennasignal processing technologies and multiple access technologies, whileobtaining a very high antenna gain by performing analog beamforming withthe use of a large number of antennas.

Another aspect of the present invention is to provide a method andapparatus for supporting both digital multi-antenna technology andanalog beamforming by means of integrated signal processingarchitecture.

Another aspect of the present invention is to provide a method andapparatus for transmitting and receiving user data and control signalsto support both digital multi-antenna technology and analog beamforming.

In accordance with an aspect of the present invention, a method fortransmitting a signal in a multi-antenna system is provided. The methodincludes a beam assignment process of designating an analog beam foreach antenna port of a plurality of antenna ports to a plurality ofmodulation symbol sequences generated to correspond to the plurality ofantenna ports, a beam multiplexing process of multiplexing signals, towhich a beam is designated by the beam assignment process, to aplurality of beam groups each having the same antenna beam combination,a resource mapping process of mapping beam group signals generated bythe beam multiplexing process, to at least one Orthogonal FrequencyDivision Multiplexing (OFDM) symbol and at least one time-frequencyresource, an OFDM generation process of generating OFDM symbol signalscorresponding to one or more antenna beams by OFDM-converting the beamgroup signals according to the resource mapping, a conversion process ofconverting the OFDM symbol signals into analog Radio Frequency (RF)signals, and a transmission process of transmitting the analog RFsignals via a plurality of antenna elements by carrying the analog RFsignals on associated antenna beams via analog beamforming.

In accordance with another aspect of the present invention, an apparatusfor transmitting a signal in a multi-antenna system is provided. Theapparatus includes a beam assignment unit for designating an analog beamfor each antenna port of a plurality of antenna ports to a plurality ofmodulation symbol sequences generated to correspond to the plurality ofantenna ports, a beam multiplexer for multiplexing signals, to which abeam is designated by the beam assignment unit, to a plurality of beamgroups each having the same antenna beam combination, a resource mapperfor mapping beam group signals generated by the beam multiplexing, to atleast one OFDM symbol and at least one time-frequency resource, an OFDMgeneration unit for generating OFDM symbol signals corresponding to oneor more antenna beams by OFDM-converting the beam group signalsaccording to the resource mapping, a conversion unit for converting theOFDM symbol signals into analog RF signals, and an analog beamformingunit for transmitting the analog RF signals via a plurality of antennaelements by carrying the analog RF signals on associated antenna beamsvia analog beamforming.

In accordance with another aspect of the present invention, an apparatusfor receiving a signal in a multi-antenna system is provided. Theapparatus includes a plurality of antenna elements for receiving signalsfrom one or more receivers, low-noise-amplifiers forlow-noise-amplifying the received signals, a switching unit forselecting a signal corresponding to at least one reception beam selectedby digital processing from among the amplified signals, for eachindividual antenna element, a phase shifting unit for outputting aplurality of reception beam signals by applying phase shift valuesdetermined by a digital processing unit, to the selected signal, and aconversion unit for converting the reception beam signals into digitalbeam signals, and transferring the digital beam signals to the digitalprocessing unit.

In accordance with another aspect of the present invention, an apparatusfor receiving a signal in a multi-antenna system is provided. Theapparatus includes a plurality of antenna elements for receiving signalsfrom one or more receivers, low-noise-amplifiers forlow-noise-amplifying the received signals, a phase shifting unit foroutputting a plurality of reception beam signals by applying phase shiftvalues determined by a digital processing unit, to the amplifiedsignals, and a conversion unit for converting the reception beam signalsinto digital beam signals, and transferring the digital beam signals tothe digital processing unit.

In accordance with another aspect of the present invention, an apparatusfor receiving a signal in a multi-antenna system is provided. Theapparatus includes a plurality of directional antenna elements arrangedin different directions, for receiving signals from one or morereceivers, low-noise-amplifiers for low-noise-amplifying the receivedsignals, a switching unit for selecting at least one of the amplifiedsignals as a reception beam, for each individual antenna element, and aconversion unit for converting the selected signal into digital beamsignals and transferring the digital beam signals to the digitalprocessing unit.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIGS. 1A and 1B schematically show a transmission structure of amulti-antenna system by digital signal processing according to anexemplary embodiment of the present invention;

FIG. 1C schematically shows a transmission structure for performinganalog beamforming according to an exemplary embodiment of the presentinvention;

FIG. 2 shows a structure of a transceiver according to an exemplaryembodiment of the present invention;

FIGS. 3 and 4 show transmission structures for simultaneouslytransmitting a plurality of antenna beams using multiple antennasaccording to exemplary embodiments of the present invention;

FIG. 5 shows a structure of a transmit Radio Frequency (RF) chain and anantenna unit for analog beamforming according to an exemplary embodimentof the present invention;

FIG. 6 shows a structure of a transmit modem for digital signalprocessing in a multi-antenna system according to an exemplaryembodiment of the present invention;

FIG. 7 shows an operation of a resource mapper according to an exemplaryembodiment of the present invention;

FIG. 8 shows a structure of a receiving modem for multi-beam digitalsignal processing according to an exemplary embodiment of the presentinvention;

FIGS. 9 and 10 show reception structures for multi-beam analogprocessing according to exemplary embodiments of the present invention;

FIG. 11 shows a resource structure for transmitting signals according toan exemplary embodiment of the present invention;

FIG. 12 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,1,1,J_(T)) according to an exemplary embodimentof the present invention;

FIG. 13 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,1,2,J_(T)/2) according to an exemplaryembodiment of the present invention;

FIG. 14 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,1,4,J_(T)/4) according to an exemplaryembodiment of the present invention;

FIG. 15 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,2,2,J_(T)/2) according to an exemplaryembodiment of the present invention;

FIG. 16 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,2,4,J_(T)/4) according to an exemplaryembodiment of the present invention;

FIG. 17 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,4,4,J_(T)/4) according to an exemplaryembodiment of the present invention;

FIG. 18 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(2,2,2,J_(T)/2) according to an exemplaryembodiment of the present invention;

FIG. 19 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(2,2,4,J_(T)/4) according to an exemplaryembodiment of the present invention; and

FIG. 20 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(2,4,4,J_(T)/4) according to an exemplaryembodiment of the present invention.

Throughout the drawings, the same drawing reference numerals will beunderstood to refer to the same elements, features and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

New technology for efficiently supporting both multi-antenna technologyby digital signal processing and analog beamforming (or Radio Frequency(RF) beamforming) in a communication system will be described below.

FIGS. 1A and 1B schematically show a transmission structure of amulti-antenna system by digital signal processing according to anexemplary embodiment of the present invention.

Referring to FIG. 1A, N_(cw) codewords are input to and encoded byN_(cw) encoders 110-1˜110-N_(cw), respectively. Output bits of theencoders 110-1˜110-N_(cw) are scrambled by scramblers 120-1˜120-N_(cw),and mapped to modulation symbols by modulation mappers 130-1˜130-N_(cw).The modulation symbols are mapped to v layers by a layer mapper 140. Aprecoder 150 maps v layer signals to P signals corresponding to Pantenna ports by a predetermined precoder. P resource mappers160-1˜160-P map the precoded signals to predetermined time-frequencyresources, and Orthogonal Frequency Division Multiplexing (OFDM)generators 170-1˜170-P convert outputs of the resource mappers160-1˜160-P into P OFDM symbol signals corresponding to P antenna ports.

Referring to FIG. 1B, an antenna mapper 180 maps P OFDM symbol signalscorresponding to antenna ports, to N_(T) Digital to Analog Converters(DACs) 190-1˜190-N_(T) corresponding to N_(T) actual antennas accordingto predetermined rules. The analog signals output from the DACs190-1˜190-N_(T) are converted into signals in an RF band which is afrequency band desired by mixers 192-1˜192-N_(T), and radiated into theair by antennas 196-1˜196-N_(T) after being power-amplified by PowerAmplifiers (PAs) 194-1˜194-N_(T).

FIG. 1C schematically shows a transmission structure for performinganalog beamforming according to an exemplary embodiment of the presentinvention.

Referring to FIG. 1C, a DAC 100 converts a digital signal, to betransmitted, into an analog signal, and the analog signal is convertedinto an RF signal by a mixer 102. The RF signal forms antenna beams bybeing phase-adjusted by individual phase shift values w1˜wN_(T) by phaseadjusters 104-1˜104-N_(T) corresponding to N_(T) Antenna Elements(ANT_E) 108-1˜108-N_(T), respectively. The outputs of the phaseadjusters 104-1˜104-N_(T) are radiated into the air by the antennaelements 108-1˜108-N_(T) after being power-amplified by power amplifiers106-1˜106-N_(T). The number of, and the directions and intensities ofthe antenna beams which are radiated into the air are controlled by thephase shift values.

An exemplary transceiver structure is disclosed below, which may obtaina very high antenna gain by performing analog beamforming using a largenumber of antennas, and may also increase the communication performanceby flexibly coping with a variety of user and channel environments withthe use of various digital multi-antenna signal processing technologiesand multiple access technologies.

FIG. 2 shows a structure of a transceiver according to an exemplaryembodiment of the present invention.

Referring to FIG. 2, the transceiver includes a controller 200, a beamselector 210, an antenna unit 220, a transmitting part 230, and areceiving part 240. The controller 200 controls beams, which aretransmitted and received by the transceiver. For example, if an optimalanalog reception beam for receiving a signal transmitted by an opponentnode is selected, the controller 200 controls the beam selector 210 toreceive the signal by forming the selected optimal analog receptionbeam. As another example, if an opponent node selects an optimal analogtransmission beam for receiving a signal from the transceiver, andannounces the selected optimal analog transmission beam by providingfeedback information, then the controller 200 controls the beam selector210 to transmit a signal by forming the selected optimal analogtransmission beam.

As another example, if it is desired to simultaneously receive signalsfrom an opponent node via a plurality of analog reception beams(J_(R)>1), the controller 200 selects a plurality of optimal analogreception beams, and controls the beam selector 210 to receive thesignals by forming the plurality of analog reception beams.

As another example, in a case where the transceiver transmits a signalsimultaneously through a plurality of analog transmission beams(J_(T)>1), if an opponent node selects a plurality of analogtransmission beams and announces the selection by providing feedbackinformation, then the controller 200 controls the beam selector 210 totransmit the signal by forming the plurality of analog transmissionbeams selected by the opponent node. As another example, in a case wherethe transceiver transmits a signal simultaneously through a plurality ofanalog transmission beams (J_(T)>1), if a plurality of opponent nodesselect one or more analog transmission beams and announce the selectionby providing feedback information, then the controller 200 controls thebeam selector 210 to transmit the signal by forming one or more analogtransmission beams selected by the plurality of opponent nodes.

The beam selector 210 transfers selected beam pattern information to thetransmitting part 230 during transmission beamforming, and transfersselected beam pattern information to the receiving part 240 duringreception beamforming.

The antenna unit 220 includes a plurality of antenna elements. Forexample, the antenna unit 220 may include a plurality of omnidirectionalantenna elements as shown in FIG. 3 or FIG. 4. As another example, theantenna unit 220 may include a plurality of directional antenna elementsfor transmitting their associated signals in different directions, asshown in FIG. 5.

The transmitting part 230 includes a transmit modem 232 and a transmitRF chain 234.

The transmit modem 232 encodes and modulates the data to be transmittedvia the antenna unit 220, converts the modulated signal into an analogsignal, and transfers the analog signal to the transmit RF chain 234.The analog signal is a baseband signal.

The transmit RF chain 234 includes a plurality of RF paths fortransferring signals to their associated antenna elements. The transmitRF chain 234 may use only some antenna elements and some RF pathsdepending on the beam pattern and beam width selected by the beamselector 210.

The transmit RF chain 234 multiplexes the baseband signals provided fromthe transmit modem 232 to at least one activated RF path, and in each RFpath, the transmit RF chain 234 converts the baseband signal into an RFsignal, and transmits the RF signal via the antenna unit 220. Thetransmit RF chain 234 controls the baseband signal such that it may forma beam depending on the beam pattern selected by the beam selector 210.For example, if the antenna unit 220 includes a plurality ofomnidirectional antenna elements as shown in FIG. 3 or FIG. 4, thetransmit RF chain 234 includes a phase shifting unit for shifting aphase of the signal transmitted via an RF path for each antenna element.Each phase shifter constituting the phase shifting element shifts aphase of the signal to be transmitted via each antenna element dependingon the beam pattern and beam width selected by the beam selector 210.The transmit RF chain 234 may obtain additional freedom in adjusting thepattern and width of the beam by adjusting a power amplification unit,an example of which is illustrated in FIG. 3 or a switching unit, anexample of which is illustrated in FIG. 4.

As another example, if the antenna unit 220 includes a plurality ofdirectional antenna elements as shown in FIG. 5, the transmit RF chain234 includes switches that connect the transmit modem 232 to antennaelements depending on the beam pattern. Each of the switches connectsthe transmit modem 232 to at least one antenna element depending on thebeam pattern and beam width selected by the beam selector 210. Eachswitch may connect the transmit modem 232 to at least one antennaelement.

The receiving part 240 includes a receive RF chain 242 and a receivemodem 244.

The receive RF chain 242 includes a plurality of RF paths for RF signalsreceived via antenna elements. The receive RF chain 242 may use onlysome antenna elements and some RF paths depending on the beam patternand beam width selected by the beam selector 210.

The receive RF chain 242 converts RF signals provided from the antennaelements into baseband signals, and transfers them to the receive modem244. The receive RF chain 242 controls the baseband signals such that itmay form a beam depending on the beam pattern selected by the beamselector 210. For example, if the antenna element 220 includes aplurality of omnidirectional antenna elements as shown in FIG. 9, thereceive RF chain 242 includes a phase shifting unit for shifting a phaseof a signal received via each antenna element. Each phase shifterincluded in the phase shifting unit shifts a phase of a signal receivedvia each antenna element depending on the beam pattern and beam widthselected by the beam selector 210.

FIGS. 3 and 4 show transmission structures for simultaneouslytransmitting a plurality of antenna beams using multiple antennasaccording to exemplary embodiments of the present invention. Each of thetransmission structures corresponds to the transmit RF chain 234 and theantenna unit 220 in FIG. 2. More specifically, a phased-array antennastructure including N_(T) antenna elements simultaneously transmitsJ_(T) antenna beams, and the antenna beams are adjusted by shiftingphases of the transmission signals.

Referring to FIG. 3, J_(T) digital signals y_(k) ^(j) (where j=1, . . ., J_(T)), which are to be simultaneously transmitted via J_(T) beams,are converted into analog signals y^(j) (t) (where j=1, . . . J_(T)) byJ_(T) DACs 310-1˜310-J_(T), and mixers 320-1˜320-J_(T) convert theanalog signals into transmission signals in a desired transmissionfrequency band by multiplying the analog signals by a carrier frequency.In order to be transferred to N_(T) antenna elements 370-1˜370-N_(T),transmission signals for individual beams are phase-shifted to matchwith the associated beams by the phase shifting unit 330. For example,transmission signals for a beam j are phase-shifted by a j-th phaseshifter set among J_(T) phase shifter sets included in the phaseshifting unit 330. The j-th phase shifter set includes N_(T) phaseshifters, and shifts a phase of the transmission signals for the beam jby w₁ ^(j), . . . , w_(NT) ^(j).

The power amplification unit 340 includes J_(T)*N_(T) power amplifiersthat correspond to beams and antennas and receive the outputs from thephase shifters. The power amplification unit 340 amplifies input signalsand adjusts levels thereof individually for each beam and each antenna.For example, N_(T) phase-shifted signals corresponding to a beam j areconverted into signals z₁ ^(j) (t), . . . , z_(NT) ^(j) (t) as theirsignal levels are adjusted by g₁ ^(j), . . . , g_(NT) ^(j),respectively. Some transmission signals may be blocked by setting theirpower control values g_(n) ^(j) to zero (0).

Summers 350-1˜350-N_(T) sum up J_(T) power-amplified signals for eachantenna element, and the antenna elements 370-1˜370-N_(T) transmit intothe air the signals transferred from the summers 350-1˜350-N_(T),respectively. A signal transmitted from an antenna element n (where n=1,. . . , N_(T)) is defined as Equation (1) below.

$\begin{matrix}{{z_{n}(t)} = {\overset{J_{T}}{\underset{j = 1}{Q}}{z_{n}^{j}(t)}}} & {{Equation}\mspace{14mu} (1)}\end{matrix}$

In the transmission structure, the width and direction of transmissionbeams are changed by adjusting N_(T) phase shift values w₁ ^(j), . . . ,w_(NT) ^(j) and power control values g₁ ^(j), . . . , g_(NT) ^(j).Therefore, a digital signal processing unit stores a combination ofphase shift values and power control values corresponding to the widthand direction of each beam, and designates a combination of phase shiftvalues and power control values corresponding to the width and directionof the desired beam, in the phase shifting unit 330 and the poweramplification unit 340.

Referring to FIG. 4, in another example of a transmission structure foranalog beamforming, J_(T) DACs 410-1˜410-J_(T) convert digital inputsignals, to be transmitted, into analog signals, and the analog signalsare converted into transmission signals in RF band by mixers420-1˜420-J_(T). A phase shifting unit 430 phase-shifts transmissionsignals for each beam by phase shift values designated by N_(T) phaseshifters.

The switching unit 440 transfers or blocks transmission signalscorresponding to each beam to/from summers 450-1˜450-N_(T) underpredetermined control. The summers 450-1˜450-N_(T) sum up transmissionsignals transferred from the switching unit 440 individually for eachantenna element, and input the summation results to power amplifiers460-1˜460-N_(T). The power amplifiers 460-1˜460-N_(T) amplify inputsignals corresponding to each antenna element and adjust their levels.For example, a level of a signal corresponding to an antenna element nis adjusted by gn (where n=1, . . . , N_(T)). The antenna elements470-1˜470-N_(T) transmit into the air the signals delivered from thepower amplifiers 460-1˜460-N_(T), respectively. The switching unit 440is optional.

FIG. 5 shows a structure of a transmit RF chain and an antenna unit foranalog beamforming according to an exemplary embodiment of the presentinvention.

Referring to FIG. 5, the transmission structure arranges a plurality ofdirectional antennas 550-1, 550-2, . . . , 550-N_(T) in differentdirections, and selects antennas via which signals are transmitted, withswitches 530-1, . . . , 530-J_(T), thereby adjusting the direction andwidth of each beam. Furthermore, J_(T) DACs 510-1˜510-J_(T) convertdigital input signals to be transmitted, into analog signals, and theanalog signals are converted into transmission signals in an RF band bymixers 520-1˜520-J_(T). Each of the switches 530-1, . . . , 530-J_(T)connects a transmission signal corresponding to each beam to any one ofthe N_(T) transmit antennas 550-1˜550-N_(T) under predetermined control.Power amplifiers 540-1˜540-N_(T) amplify input signals delivered via theswitching unit 530 and corresponding to the transmit antennas550-1˜550-N_(T), adjust their levels, and connect the amplified andlevel-adjusted signals to their associated transmit antennas550-1˜550-N_(T). For example, a level of a signal corresponding to anantenna element n is adjusted by gn (where n=1, . . . , N_(T)). Theantenna elements 550-1˜550-N_(T) transmit into the air the signalsdelivered from the power amplifiers 540-1˜540-N_(T).

Connection combinations between J_(T) beams and N_(T) transmit antennasare designated and stored in advance, and the switches 530-1˜530-J_(T)operate depending on the switching pattern selected to correspond to theconnection combinations. Although the power amplifiers 540-1˜540-N_(T)are assumed to be interposed between the switches 530-1˜530-J_(T) andthe transmit antennas 550-1˜550-N_(T), the power amplifiers540-1˜540-N_(T) may be interposed between the mixers 520-1˜520-J_(T) andthe switches 530-1˜530-J_(T) in an alternative exemplary embodiment.

FIG. 6 shows a structure of a transmit modem for digital signalprocessing in a multi-antenna system according to an exemplaryembodiment of the present invention.

Referring to FIG. 6, this structure uses N_(cw) transport channels foreach user, in order to transmit data to receivers (i.e., users orreceive stations) for N_(user) users. In addition, for datatransmission, v layers and P virtual antennas (i.e., antenna ports) areused for each user, and J_(T) beams may be formed for all users.Furthermore, N_(cw) codewords for each user are input to an encodingunit 610 and encoded therein by an error correcting code. A scramblingunit 620 scrambles output bits of the encoding unit 610 by multiplyingthem by a random scrambling code sequence of 0 or 1 that a receiver maygenerate. A modulation mapping unit 630 maps the scrambled bits tomodulation symbols according to the predetermined modulation scheme suchas Quadrature Amplitude Modulation (QAM) and Phase Shift Keying (PSK).

A layer mapping unit 640 maps a modulation symbol sequence for each userto a predetermined number, v, of layers, and a precoding unit 650 maps vlayer signals to P signals corresponding to P antenna ports bypredetermined coders. A beam assignment unit 660 assigns the precodedsignals from the precoding unit 650 to P beams, for each user. A beammultiplexer 670 multiplexes P*N_(user) precoded signals beam-assignedfor N_(user) users, to N_(beamgroup) beam groups depending on thesameness (or equality) of the antenna beam combination(N_(beamgroup)≦N_(user)).

A resource mapper 680 maps the beam group signals, which are generatedby the beam multiplexing, to predetermined time-frequency resources, andan OFDM generation unit 690 independently converts the outputs of theresource mapper 680 into OFDM symbol signals corresponding to J_(T)beams, and outputs the OFDM symbol signals to an analog processing unit(not shown). As an example, the analog processing unit may be configuredas shown in any one of FIGS. 3 to 5.

The signal conversion performed in FIG. 6 will be described in moredetail below.

An exemplary process of generating a scrambled bit sequence ofb′^((q))(0), . . . , b′^((q))(M_(bit) ^((q))−1), which is the resultobtained by scrambling a coded bit sequence of b^((q))(0), . . . ,b^((q))(M_(bit) ^((q))−1), q=0, . . . , N_(cw)−1 for N_(cw) transportchannels, where M_(bit) ^((q)) denotes the number of bits for atransport channel q, is shown in Equation (2) below.

b′ ^((q))(i)=(b ^((q))(i)+c ^((q))(i))mod 2

i=0, . . . ,M _(bit) ^((q))−1,q=0, . . . ,N _(cw)−1  Equation (2)

The scrambling code sequence c^((q))(i) is generated according to thepredetermined rules agreed in advance between a transmitter and areceiver, and the predetermined rules denote, for example, informationabout an initial value of the scrambling code sequence. The initialvalue of the scrambling code sequence may be designated equally for allreceivers in the cell, but differently for each cell. In an alternativeexemplary embodiment, the initial value of the scrambling code sequencemay be designated differently for each cell and each receiver. Forexample, an initial value c_(init) of the scrambling code sequence isdesignated as shown in Equation (3) below,

c _(init) =n _(RNTI) E2¹⁴ +qE2¹³ +*n _(s)/2+E2⁹ +N _(ID)^(cell)  Equation (3)

where n_(RNTI) denotes a unique number or a Radio Network TemporaryIdentifier (RNTI) for identifying a receiver (i.e., a receive station),q denotes the number of codewords, n_(s) denotes a slot number, andN_(ID) ^(cell) denotes a physical identifier of a cell.

The scrambling allows a specific receiver for its cell to decode bits ofonly a specific codeword, prevents the decoding by another receiver forits cell, or by a receiver for another cell, and prevents the decodingfor a bit sequence of another codeword for the receiver. In addition,the scrambling may increase the performance with the same encoder anddecoder, by ensuring robustness against bit errors.

The layer mapping unit 640 converts a modulation symbol sequence ofd^((q))(0), . . . , d^((q))(M_(bit) ^((q))−1) (q=0, . . . , N_(cw)−1)for N_(cw) transport channels into v modulation symbol groups ofx⁽⁰⁾(i), . . . , x^((v-1))(i), i=0, . . . , M_(symb) ^(layer)−1, whereM_(symb) ^(layer) denotes the number of modulation symbols transmittedover each layer.

If the number, v, of layers is greater than 1, v QAM or PSK symbols aresimultaneously transmitted to a receiver via a plurality of antennaswith the same time and frequency resources, guaranteeing SpatialMultiplexing (SM) gain by which a data rate increases v times, comparedto when only one symbol is transmitted. Layer mapping may be performedas shown in, for example, Table 1 below.

TABLE 1 Number of Number of Codewords Layers (v) (N_(cw)) Codeword-LayerMapping 1 1 X⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ 2 1X⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/2 X⁽¹⁾(i) =d⁽⁰⁾(2i + 1) 2 2 X⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ =X⁽¹⁾(i) = d⁽¹⁾(i) M_(symb) ⁽¹⁾ 3 1 X⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer)= M_(symb) ⁽⁰⁾/3 X⁽¹⁾(i) = d⁽¹⁾(3i + 1) X⁽²⁾(i) = d⁽²⁾(3i + 2) 3 2X⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ = X⁽¹⁾(i) = d⁽¹⁾(2i)M_(symb) ⁽¹⁾/2 X⁽²⁾(i) = d⁽¹⁾(2i + 1) 4 1 X⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/4 X⁽¹⁾(i) = d⁽¹⁾(4i + 1) X⁽²⁾(i) = d⁽²⁾(4i + 2)X⁽³⁾(i) = d⁽³⁾(4i + 3) 4 2 X⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/2 = X⁽¹⁾(i) = d⁽⁰⁾(2i + 1) M_(symb) ⁽¹⁾/2 X⁽²⁾(i) =d⁽¹⁾(2i) X⁽³⁾(i) = d⁽¹⁾(2i + 1) 5 2 X⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer)= M_(symb) ⁽⁰⁾/2 = X⁽¹⁾(i) = d⁽⁰⁾(2i + 1) M_(symb) ⁽¹⁾/3 X⁽²⁾(i) =d⁽¹⁾(3i) X⁽³⁾(i) = d⁽¹⁾(3i + 1) X⁽⁴⁾(i) = d⁽¹⁾(3i + 2) 6 2 X⁽⁰⁾(i) =d⁽⁰⁾(3i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3 = X⁽¹⁾(i) = d⁽⁰⁾(3i + 1)M_(symb) ⁽¹⁾/3 X⁽²⁾(i) = d⁽⁰⁾(3i + 2) X⁽³⁾(i) = d⁽¹⁾(3i) X⁽⁴⁾(i) =d⁽¹⁾(3i + 1) X⁽⁵⁾(i) = d⁽¹⁾(3i + 2) 7 2 X⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/3 = X⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽¹⁾/4X⁽²⁾(i) = d⁽⁰⁾(3i + 2) X⁽³⁾(i) = d⁽¹⁾(4i) X⁽⁴⁾(i) = d⁽¹⁾(4i + 1) X⁽⁵⁾(i)= d⁽¹⁾(4i + 2) X⁽⁶⁾(i) = d⁽¹⁾(4i + 3) 8 2 X⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/4 = X⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽¹⁾/4X⁽²⁾(i) = d⁽⁰⁾(4i + 2) X⁽³⁾(i) = d⁽⁰⁾(4i + 3) X⁽⁴⁾(i) = d⁽¹⁾(4i) X⁽⁵⁾(i)= d⁽¹⁾(4i + 1) X⁽⁶⁾(i) = d⁽¹⁾(4i + 2) X⁽⁷⁾(i) = d⁽¹⁾(4i + 3)

The precoding unit 650 permutes layer-mapped modulation symbol groupsaccording to the predetermined rules or multiplies them by a precodingmatrix (also called a precoder), and if necessary, converts them intosignal groups of y₍₀₎(i), . . . , y^((P-1))(i), i=0, . . . , M_(symb)^(ap)−1 each consisting of P signals having complex values by adding aCyclic Delay Diversity (CDD) code. Here, M_(symb) ^(ap) denotes thenumber of modulation symbols transferred to each antenna port.

The precoded signals are mapped to antenna ports or virtual antennas. Ifthe number, P, of antenna ports is the same as the number, v, of layersand is greater than 1, Single User-Multiple Input Multiple Output(SU-MIMO) is supported, which transmits data of P=v transport channelsto a single user via P antenna ports. If P>v, the transmit antennadiversity effect or the digital transmit antenna beamforming effect maybe obtained by the precoding. For example, precoding may be shown as inEquation (4) below.

$\begin{matrix}{\begin{bmatrix}y^{(0)} & (i) \\\vdots & \; \\y^{({P - 1})} & (i)\end{bmatrix} = {{W(i)}\begin{bmatrix}x^{(0)} & (i) \\\vdots & \; \\x^{({\upsilon - 1})} & (i)\end{bmatrix}}} & {{Equation}\mspace{14mu} (4)}\end{matrix}$

An example of precoding that adds CDD may be shown as in Equation (5)below.

$\begin{matrix}{\begin{bmatrix}y^{(0)} & (i) \\\vdots & \; \\y^{({P - 1})} & (i)\end{bmatrix} = {{W(i)}{D(i)}{U\begin{bmatrix}x^{(0)} & (i) \\\vdots & \; \\x^{({\upsilon - 1})} & (i)\end{bmatrix}}}} & {{Equation}\mspace{14mu} (5)}\end{matrix}$

In Equation (5), W(i) notes a precoding matrix with a size of P*v, D(i)denotes a matrix with a size of v*v, used to support CDD, and U denotesa matrix with a size of v*v, which is given in advance to supportdifferent numbers of layers.

The matrixes D(i) and U may be determined as shown in, for example,Table 2 below.

TABLE 2 (v) U D(i) 2 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 & 1 \\1 & e^{{- j}\; 2{\pi/2}}\end{bmatrix}$ $\quad\begin{bmatrix}1 & 0 \\0 & e^{{- j}\; 2{\pi/2}}\end{bmatrix}$ 3 $\frac{1}{\sqrt{3}}\begin{bmatrix}1 & 1 & 1 \\1 & e^{{- {j2}}\; {\pi/3}} & e^{{- j}\; 4{\pi/3}} \\1 & e^{{- j}\; 4{\pi/3}} & e^{{- j}\; 8{\pi/3}}\end{bmatrix}$ $\quad\begin{bmatrix}1 & 0 & 0 \\0 & e^{{- j}\; 2{\pi/3}} & 0 \\0 & 0 & e^{{- j}\; 4{\pi/3}}\end{bmatrix}$ 4 $\frac{1}{2}\begin{bmatrix}1 & 1 & 1 & 1 \\1 & e^{{- j}\; 2{\pi/4}} & e^{{- j}\; 4{\pi/4}} & e^{{- j}\; 6{\pi/4}} \\1 & e^{{- j}\; 4{\pi/4}} & e^{{- j}\; 8{\pi/4}} & e^{{- j}\; 12{\pi/4}} \\1 & e^{{- j}\; 6{\pi/4}} & e^{{- j}\; 12{\pi/4}} & e^{{- j}\; 18{\pi/4}}\end{bmatrix}$ $\quad\begin{bmatrix}1 & 0 & 0 & 0 \\0 & e^{{- j}\; 2{\pi/4}} & 0 & 0 \\0 & 0 & e^{{- j}\; 4{\pi/4}} & 0 \\0 & 0 & 0 & e^{{- j}\; 6{\pi/4}}\end{bmatrix}$

The beam assignment unit 660 designates an antenna beam φ(u,p) (whereu=0, 1, . . . ,N user−1, and p=0, 1, . . . , P−1) that will transmit asignal for each antenna port p for each receiver u. If the beamassignment unit 660 selects an antenna beam, phase shift values (in FIG.3 or FIG. 4) are selected or a switching pattern (in FIG. 5) is selectedin the analog processing unit depending on the selected beam. Theantenna beam may be selected based on the results that a receiver feedsback by measuring a level of a received signal.

The beam multiplexer 670 multiplexes the signals in the same antennabeam combination among the precoded signals for N_(user) receivers, tothe same beam group. The beam group made by the multiplexing may berepresented as φ(u′)={φ(u′,p)|p=0, 1, . . . , P−1}, and u′=0, 1, . . . ,N_(beamgroup)−1. By multiplexing the precoded signals for the usersusing the same antenna beam combination, to the same beam group, thetransmission structure may designate a plurality of user signals by FDMin the same resource assignment time. More specifically, an antenna beamcombination including P antenna beams is assigned to each user, and thebeam multiplexer 670 compares antenna beam combinations for users witheach other, and multiplexes signals for the users whose P antenna beamsare all the same, to one beam group.

For P>v, especially for P=mv (where m=2, 3, . . . ), the transmissionstructure may transmit signals for m users with the same frequencyand/or same beam group for the same time by applying Multi-User(MU)-MIMO technology. An optimal precoding matrix for MU-MIMO may beobtained by applying a variety of conventional MU-MIMO technologies. Inother words, the beam multiplexer 670 may support optimized resourceassignment by simultaneously assigning resources to multiple users thatuse the same beam group, by FDM or MU-MIMO.

For transmission over J_(T) antenna beams, the resource mapper 680assigns time and frequency resources, corresponding to J_(T) OFDMsymbols, to its input signals, where J_(T)≧P. Depending on the resourceassignment unit, the resources of OFDM symbols may be assigned in unitsof individual OFDM symbols, or in units of slots each consisting of aplurality of OFDM symbols. In this way, the resource mapper 680 maybasically support TDM that assigns time resources in units of slots orOFDM symbols. More specifically, the signals, which are classified asthe same beam group by beam multiplexing. are mapped to OFDM symbols inthe same (slot) time. Signals belonging to different beam groups aremapped to OFDM symbols in different (slot) times, or mapped to differentresources in the same slot or OFDM symbol time. Interference between thesimultaneously transmitted beams needs to be minimized.

For J_(T)=P, signals of only one beam group may be transmitted. In thiscase, FDM or MU-MIMO is supported. For J_(T)>P, especially for J_(T)=mP(where m=2, 3, . . . ), Spatial Division Multiplexing (SDM) isadditionally supported, which transmits signals to multiple users withdifferent beams in the same time and frequency. The transmissionstructure shown in FIG. 6 has the conditions of J_(T)=P*N_(sdm), whereN_(sdm) denotes the number of beam groups which are transmitted by SDMfor the same resource assignment time.

FIG. 7 shows an operation of a resource mapper according to an exemplaryembodiment of the present invention.

Referring to FIG. 7, when a Transmit Time Interval (TTI) or slot definedas a resource assignment period starts, a scheduler (not shown, butincluded in the resource mapper by way of example) designates prioritiesof beam groups by performing scheduling according to a predeterminedscheduling algorithm, in step 712. Signals in each beam group have thesame antenna beam combination, and beam groups are indexed in order ofthe priority by scheduling.

In step 714, parameters for the resource assignment algorithm areinitialized. For example, a transmission beam set Ω is initialized to anempty set of { }, a beam group index u′ is initialized to zero (0), andan OFDM symbol index j is initialized to zero (0).

In step 716, the resource mapper designates a new candidate transmissionbeam group φ(u′) by a beam group index u′ as φ(u′,0), . . . , φ(u′,P−1).In step 718, the resource mapper determines if the new candidatetransmission beam group includes beams that are totally different fromthose in the selected existing transmission beam set Ω. If the newcandidate transmission beam group includes only the completely new beamswhich are different from the selected existing beams, the resourcemapper determines in step 720 whether interference between the newcandidate transmission beam group and the selected existing transmissionbeam set is less than a predetermined reference value. If theinterference between the beams is less than the reference value, theresource mapper assigns resource blocks of OFDM symbols j, . . . , j+P−1to transmit signals yφ(u′,0), . . . , yφ(u′,P−1) of φ(u′,0), . . . ,φ(u′,P−1) in step 722. The resource mapper adds beams in the newcandidate transmission beam group φ(u′) to the transmission beam set Ω,in step 724, increases the OFDM symbol index by P in step 726 (j=j+P),and increases the beam group index by 1 in step 728 (u′u′+1).

On the other hand, if one or more beams in the new candidate beam groupoverlap with the selected existing beams in step 718, the resourcemapper directly proceeds to step 728. Also, if interference between thebeams is not less than the reference value in step 720, the resourcemapper directly proceeds to step 728.

In step 730, the resource mapper determines whether it has assignedresources of all assignable OFDM symbols (j≧J_(T)), or whether it hasconsidered transmission of all candidate transmission beam groups(u′≧N_(beamgroup)). If so, resource assignment for a given TTI or slotis completed. If not, the resource mapper returns to step 716.

The resource assignment algorithm of FIG. 7 may be modified in variousdifferent ways. As an example, in step 720, the resource assignmentalgorithm may optimize a precoding unit to minimize inter-beaminterference, to maximize its signal level, or to maximize a sum rate.As another example, the resource assignment algorithm may employ avariety of conventional optimization technologies.

FIG. 8 shows a structure of a receive modem for multi-beam digitalsignal processing according to an exemplary embodiment of the presentinvention.

Referring to FIG. 8, J_(R) reception beams received via a receiveantenna unit (not shown) are received at a synchronizer 810 and J_(R)OFDM receivers 820-1˜820-J_(R). The synchronizer 810 acquiressynchronization of a transmitter using the reception beams, and providesinformation about the synchronization to the OFDM receivers820-1˜820-J_(R). The OFDM receivers 820-1˜820-J_(R) output J_(R) OFDMsymbol signals by individually performing OFDM reception processing ondigital signals received through the J_(R) reception beams according tothe synchronization.

A receive filter 830 obtains v received signals transmitted from atransmitter and corresponding to v layers by performing receptionfiltering processing on the J_(R) OFDM symbol signals. Although notillustrated, if J_(R)>v, digital reception beamforming technology may beadditionally applied for the v signals. A resource demapper 840 performspermutation so that a decoder 850 may process the received signals. Thedecoder 850 obtains bit streams (i.e., codewords) for N_(cw) transportchannels by decoding the received signals delivered from the resourcedemapper 840. The receive filter 830 and the resource demapper 840 areinterchangeable with each other in terms of position.

FIGS. 9 and 10 show reception structures for multi-beam analogprocessing according to exemplary embodiments of the present invention.

Referring to FIG. 9, signals, which are simultaneously received viaN_(R) antenna elements 910-1˜910-N_(R), are received as J_(R) beamsthrough analog reception beamforming by a switching unit 930 and a phaseshifting unit 940 after passing through N_(R) Low Noise Amplifiers(LNAs) 920-1˜920-N_(R). More specifically, the switching unit 930includes N_(R)*J_(R) switches, and for each antenna element, selectivelyinputs its received signals to associated J_(R) phase shifters includedin the phase shifting unit 940 by on/off controlling the receivedsignals. The phase shifting unit 940, using the individual phaseshifters, outputs J_(R) reception beam signals by applying phase shiftvalues w₁ ¹˜w₁ ^(JR), . . . , w_(NR) ¹˜w_(NR) ^(JR) determined by adigital processing unit, to the signals received via the switching unit930. The J_(R) signals output by the phase shifting unit 940 are inputto J_(R) mixers 950-1˜950-J_(R). The J_(R) mixers 950-1˜950-J_(R)combine the J_(R) signals received from the phase shifting unit 940, andoutput the mixed signals to the J_(R) ADCs 960-1˜960-J_(R). Thereception beam signals are converted into digital reception beam signalsby the ADCs 960-1˜960-J_(R). The switching unit 930 is optional.

FIG. 10 shows a reception structure that uses a plurality of directionalantennas according to an exemplary embodiment of the present invention.

Referring to FIG. 10, N_(R) directional antenna elements1010-1˜1010-N_(R) are arranged in different directions depending on thepredetermined gap and positions. Switches 1030-1˜1030-J_(R) adjust thedirection and width of reception beams by selecting at least one antennaelement via which the reception structure is to receive a signal.Signals received via the N_(R) antenna elements 1010-1˜1010-N_(R) arereceived as J_(R) reception beam signals by means of J_(R) switches1030-1˜1030-J_(R) after passing through N_(R) LNAs 1020-1˜1020-N_(R).Each switch connects one or more different received signals among theN_(R) received signals that have passed through the LNAs1020-1˜1020-N_(R), to one of mixers 1040-1˜1040-J_(R). The J_(R) mixers1040-1˜1040-J_(R) frequency-convert RF reception beam signals receivedvia the switches 1030-1˜1030-J_(R) into baseband signals, and thebaseband signals are converted into digital signals by J_(R) ADCs1050-1˜1050-J_(R) and transferred to a receive modem.

FIG. 11 shows a resource structure for transmitting signals according toan exemplary embodiment of the present invention.

Referring to FIG. 11, 10 OFDM symbols may be transmitted with each beamin every slot or every TTI. Resources are assigned in one slot in unitsof 10 OFDM symbols. In each slot, 10 OFDM symbols are transmittedthrough the same beam. Each of the OFDM symbols may occupy ksubcarriers. In an alternative exemplary embodiment, the beam may beswitched in every OFDM symbol.

FIGS. 12 to 20 show combinations of analog beamforming and digitalantenna signal processing structures supportable for J_(T)=4 accordingto exemplary embodiments of the present invention, where J_(T) denotesthe number of transmission beams. The illustrated exemplary structuressupport both TDM and FDM, and additionally support SDM forN_(sdm)=J_(T)/P and MU-MIMO for P/v users.

FIGS. 12 to 17 show structures for N_(cw)=1 indicating that onetransport channel is used for each user.

FIG. 12 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,1,1,J_(T)) according to an exemplary embodimentof the present invention. In the illustrated example, this transmissionstructure simultaneously transmits signals to J_(T)=4 users by SDM.

Referring to FIG. 12, N_(user) codewords for N_(user) users areindividually encoded by an error correcting code in an encoding unit1210. A scrambling unit 1220 scrambles the output bits of the encodingunit 1210 by multiplying them by a scrambling code sequence, and amodulation mapping unit 1230 maps the scrambled bits to modulationsymbols according to the predetermined modulation scheme.

A layer mapping unit 1240 maps a modulation symbol sequence for eachuser to one associated layer, and a precoding unit 1250 maps each layersignal to one antenna port signal by a predetermined precoder. A beamassignment unit 1260 assigns one beam to each precoded signal from theprecoding unit 1250, and a beam multiplexer 1270 multiplexes thesignals, beam-assigned for N_(user) users, to N_(beamgroup) beam groupsdepending on the sameness of the antenna beam combination.

A resource mapper 1280 maps the beam-multiplexed signals topredetermined time-frequency resources, and OFDM generators1290-1˜1290-J_(T) individually convert the outputs of the resourcemapper 1280 into OFDM symbol signals corresponding to J_(T) beams andoutput the OFDM symbol signals to an analog processing unit (not shown).

In the structure shown, the layer mapping unit 1240 and the precodingunit 1250 are optional, because a signal for each user corresponds toone layer and one layer port.

FIG. 13 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,1,2,J_(T)/2) according to an exemplaryembodiment of the present invention. In the illustrated example, thistransmission structure may simultaneously provide digital beamforming byprecoding for P=2, to J_(T)/2=2 users by SDM.

Referring to FIG. 13, N_(user) codewords for N_(user) users areindividually encoded by an error correcting code in an encoding unit1310. A scrambling unit 1320 scrambles the output bits of the encodingunit 1310 by multiplying them by a scrambling code sequence, and amodulation mapping unit 1330 maps the scrambled bits to modulationsymbols according to the predetermined modulation scheme.

A layer mapping unit 1340 maps a modulation symbol sequence for eachuser to one associated layer, and a precoding unit 1350 maps each layersignal to two antenna port signals by a predetermined precoder. A beamassignment unit 1360 assigns one beam to each precoded signal from theprecoding unit 1350, and a beam multiplexer 1370 multiplexes 2*N_(user)signals beam-assigned for N_(user) users, to N_(beamgroup) beam groupsdepending on the sameness of the antenna beam combination.

A resource mapper 1380 maps the beam-multiplexed signals topredetermined time-frequency resources, and OFDM generation units1390-1˜1390-J_(T) convert the outputs of the resource mapper 1380 intoOFDM symbol signals corresponding to J_(T) beams, respectively, andoutput the OFDM symbol signals to an analog processing unit.

This structure may transmit a 1-layer signal to a total of 4 stations,since it may simultaneously support not only SDM but also 1-layerMU-MIMO, for two stations by precoding for P=2. For similar reasons asdescribed with reference to FIG. 12, the layer mapping unit 1340 isoptional.

FIG. 14 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,1,4,J_(T)/4) according to an exemplaryembodiment of the present invention. In the illustrated example, thistransmission structure provides digital beamforming to J_(T)/4=1 user byprecoding for P=4. In addition, this structure may support layer-1MU-MIMO for four users.

Referring to FIG. 14, N_(user) codewords for N_(user) users areindividually encoded by an error correcting code in an encoding unit1410. A scrambling unit 1420 scrambles the output bits of the encodingunit 1410 by multiplying them by a scrambling code sequence, and amodulation mapping unit 1430 maps the scrambled bits to modulationsymbols according to the predetermined modulation scheme.

A layer mapping unit 1440 maps a modulation symbol sequence for eachuser to one associated layer, and a precoding unit 1450 maps each layersignal to 4 antenna port signals by a predetermined precoder. A beamassignment unit 1460 assigns one beam to each precoded signal from theprecoding unit 1450, and a beam multiplexer 1470 multiplexes 4*N_(user)signals beam-assigned for N_(user) users, to N_(beamgroup) beam groupsdepending on the sameness of the antenna beam combination.

A resource mapper 1480 maps the beam-multiplexed signals topredetermined time-frequency resources, and OFDM generation units1490-1˜1490-J_(T) convert the outputs of the resource mapper 1480 intoOFDM symbol signals corresponding to J_(T) beams, respectively, andoutput them to an analog processing unit.

Although the transmission structure in FIG. 14 obtains results similarto the structure of FIG. 12, the transmission structure in FIG. 14 isdifferent from the transmission structure in FIG. 12 in terms of theantenna beam selection and precoder optimization process. For thesimilar reasons, the layer mapping unit 1440 is optional.

FIG. 15 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,2,2,J_(T)/2) according to an exemplaryembodiment of the present invention. In the illustrated example, thistransmission structure simultaneously transmits signals to two users bySDM, and provides SM SU-MIMO for v=2 to each user, where v denotes thenumber of layers.

Referring to FIG. 15, N_(user) codewords for N_(user) users areindividually encoded by an error correcting code in an encoding unit1510. A scrambling unit 1520 scrambles the output bits of the encodingunit 1510 by multiplying them by a scrambling code sequence, and amodulation mapping unit 1530 maps the scrambled bits to modulationsymbols according to the predetermined modulation scheme.

A layer mapping unit 1540 maps a modulation symbol sequence for eachuser to two layers, and a precoding unit 1550 maps each layer signal toone antenna port signal by a predetermined precoder. The transmissionstructure transmits two modulation symbols to each user with each timeand frequency resource, since the number of layers for each user is v=2.A beam assignment unit 1560 assigns one beam to each precoded signalfrom the precoding unit 1550, and a beam multiplexer 1570 multiplexes2*N_(user) signals beam-assigned for N_(user) users, to N_(beamgroup)beam groups depending on the sameness of the antenna beam combination.

A resource mapper 1580 maps the beam-multiplexed signals topredetermined time-frequency resources, and OFDM generation units1590-1˜1590-J_(T) convert the outputs of the resource mapper 1580 intoOFDM symbol signals corresponding to J_(T) beams, respectively, andoutput them to an analog processing unit (not shown).

FIG. 16 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,2,4,J_(T)/4) according to an exemplaryembodiment of the present invention. In the illustrated example, thistransmission structure supports SM SU-MIMO for v=2 for one user witheach time and frequency resource, where v denotes the number of layers,and additionally provides not only analog beamforming but also digitalbeamforming by precoding. In addition, the illustrated exemplarytransmission structure may provide 2-layer MU-MIMO to two users witheach time and frequency resource. In this case, this transmissionstructure is the same in data rate, compared with the transmissionstructure in FIG. 15 that transmits signals to two users by SDM, but thetwo transmission structures are different in terms of the antenna beamselection and precoder optimization process.

Referring to FIG. 16, N_(user) codewords for N_(user) users areindividually encoded by an error correcting code in an encoding unit1610. A scrambling unit 1620 scrambles the output bits of the encodingunit 1610 by multiplying them by a scrambling code sequence, and amodulation mapping unit 1630 maps the scrambled bits to modulationsymbols according to the predetermined modulation scheme.

A layer mapping unit 1640 maps a modulation symbol sequence for eachuser to two layers, and a precoding unit 1650 maps two layer signals tofour antenna port signals by a predetermined precoder. The transmissionstructure transmits 2 modulation symbols to each user with each time andfrequency resource since the number of layers for each user is v=2. Abeam assignment unit 1660 assigns one beam to each precoded signal fromthe precoding unit 1650, and a beam multiplexer 1670 multiplexes4*N_(user) signals beam-assigned for N_(user) users, to N_(beamgroup)beam groups depending on the sameness of the antenna beam combination.

A resource mapper 1680 maps the beam-multiplexed signals topredetermined time-frequency resources, and OFDM generation units1690-1˜1690-J_(T) convert the outputs of the resource mapper 1680 intoOFDM symbol signals corresponding to J_(T) beams, respectively, andoutput them to an analog processing unit.

FIG. 17 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(1,4,4,J_(T)/4) according to an exemplaryembodiment of the present invention. In the illustrated example, thistransmission structure provides SU-MIMO for v=4 to one user with eachtime and frequency resource, where v denotes the number layers.

Referring to FIG. 17, N_(user) codewords for N_(user) users areindividually encoded by an error correcting code in an encoding unit1710. A scrambling unit 1720 scrambles the output bits of the encodingunit 1710 by multiplying them by a scrambling code sequence, and amodulation mapping unit 1730 maps the scrambled bits to modulationsymbols according to the predetermined modulation scheme.

A layer mapping unit 1740 maps a modulation symbol sequence for eachuser to 4 layers, and a precoding unit 1750 maps each layer signal toone antenna port signal by a predetermined precoder. The transmissionstructure transmits 4 modulation symbols to each user with each time andfrequency resource since the number of layers for each user is v=4. Abeam assignment unit 1760 assigns one beam to each precoded signal fromthe precoding unit 1750, and a beam multiplexer 1770 multiplexes4*N_(user) signals beam-assigned for N_(user) users, to N_(beamgroup)beam groups depending on the sameness of the antenna beam combination.

A resource mapper 1780 maps the beam-multiplexed signals topredetermined time-frequency resources, and OFDM generation units1790-1˜1790-J_(T) convert the outputs of the resource mapper 1780 intoOFDM symbol signals corresponding to J_(T) beams, respectively, andoutput them to an analog processing unit (not shown).

FIGS. 18 to 20 show structures for N_(cw)=2 indicating that twotransport channels are used for each user.

FIG. 18 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(2,2,2,J_(T)/2) according to an exemplaryembodiment of the present invention. In the illustrated example, thistransmission structure simultaneously transmits signals to two users bySMD and supports SM SU-MIMO for v=2 for each user, where v denotes thenumber of layers.

Referring to FIG. 18, codewords for each user are individually encodedby an error correcting code in each encoder in an encoding unit 1810. Ascrambling unit 1820 scrambles the output bits of the encoding unit 1810by multiplying them by a scrambling code sequence, and a modulationmapping unit 1830 maps the scrambled bits to modulation symbolsaccording to the predetermined modulation scheme.

A layer mapping unit 1840 maps two modulation symbol sequences for eachuser to two layers, and a precoding unit 1850 maps each layer signal toone antenna port signal by a predetermined precoder. A beam assignmentunit 1860 assigns one beam to each precoded signal from the precodingunit 1850, and a beam multiplexer 1870 multiplexes 2*N_(user) signalsbeam-assigned for N_(user) users, to N_(beamgroup) beam groups dependingon the sameness of the antenna beam combination.

A resource mapper 1880 maps the beam-multiplexed signals topredetermined time-frequency resources, and OFDM generation units1890-1˜1890-J_(T) convert the outputs of the resource mapper 1880 intoOFDM symbol signals corresponding to J_(T) beams, respectively, andoutput them to an analog processing unit.

FIG. 19 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(2,2,4,J_(T)/4) according to an exemplaryembodiment of the present invention. In the illustrated example, thistransmission structure provides SM SU-MIMO for v=2 to one user with eachtime and frequency resource, where v denotes the number of layers, andadditionally provides not only analog beamforming but also digitalbeamforming by precoding. In addition, the transmission structure shownmay provide 2-layer MU-MIMO to two users with each time and frequencyresource. In this case, this transmission structure is the same in datarate, compared with the transmission structure in FIG. 18 that transmitssignals to two users by SDM, but the two transmission structures aredifferent in terms of the antenna beam selection and precoderoptimization process.

Referring to FIG. 19, codewords for each user are individually encodedby an error correcting code in an encoding unit 1910. A scrambling unit1920 scrambles the output bits of the encoding unit 1910 by multiplyingthem by a scrambling code sequence, and a modulation mapping unit 1930maps the scrambled bits to modulation symbols according to thepredetermined modulation scheme.

A layer mapping unit 1940 maps two modulation symbol sequences for eachuser to two layers, and a precoding unit 1950 maps two layer signals tofour antenna port signals by a predetermined precoder. A beam assignmentunit 1960 assigns one beam to each precoded signal from the precodingunit 1950, and a beam multiplexer 1970 multiplexes 4*N_(user) signalsbeam-assigned for N_(user) users, to N_(beamgroup) beam groups dependingon the sameness of the antenna beam combination.

A resource mapper 1980 maps the beam-multiplexed signals topredetermined time-frequency resources, and OFDM generation units1990-1˜1990-J_(T) convert the outputs of the resource mapper 1980 intoOFDM symbol signals corresponding to J_(T) beams, respectively, andoutput them to an analog processing unit (not shown).

FIG. 20 shows a transmission structure for(N_(cw),v,P,N_(sdm))=(2,4,4,J_(T)/4) according to an exemplaryembodiment of the present invention. In the illustrated example, thistransmission structure provides SM SU-MIMO for v=4 to one user with eachtime and frequency resource, where v denotes the number of layers.

Referring to FIG. 20, codewords for each user are individually encodedby an error correcting code in an encoding unit 2010. A scrambling unit2020 scrambles the output bits of the encoding unit 2010 by multiplyingthem by a scrambling code sequence, and a modulation mapping unit 2030maps the scrambled bits to modulation symbols according to thepredetermined modulation scheme.

A layer mapping unit 2040 maps two modulation symbol sequences for eachuser to two layers, and a precoding unit 2050 maps two layer signals tofour antenna port signals by a predetermined precoder. A beam assignmentunit 2060 assigns one beam to each precoded signal from the precodingunit 2050, and a beam multiplexer 2070 multiplexes 4*N_(user) signalsbeam-assigned for N_(user) users, to N_(beamgroup) beam groups dependingon the sameness of the antenna beam combination.

A resource mapper 2080 maps the beam-multiplexed signals topredetermined time-frequency resources, and OFDM generation units2090-1˜2090-J_(T) convert the outputs of the resource mapper 2080 intoOFDM symbol signals corresponding to J_(T) beams, respectively, andoutput them to an analog processing unit (not shown).

The above-described exemplary analog beamforming and digital antennasignal processing architecture may be similarly used for transmittingnot only the user data but also control information. In order to receiveits own control information, a station needs to know information aboutan initial value of a scrambling code sequence used in the scramblingunit.

As is apparent from the foregoing description, the disclosed exemplaryembodiments of the present invention may efficiently support both themulti-antenna technology by digital signal processing and the analogbeamforming. Exemplary embodiments of the present invention use a largenumber of antennas and perform analog beamforming, thereby obtaining avery high antenna gain. In addition, the invention may flexibly copewith a variety of user and channel environments by simultaneously usinga variety of digital multi-antenna signal processing and multiple accesstechnologies, contributing to an increase in system performance. Withthe use of the combined signal processing architecture, exemplaryembodiments of the present invention may provide digital beamforming ordiversity, support SU-MIMO or MU-MIMO, and provide not only TDM but alsoFDM and SDM.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for transmitting signals in amulti-antenna system, the method comprising: precoding a plurality ofmodulation symbols to generate a plurality of precoded signalscorresponding to a plurality of antenna ports for each user equipmentamong a plurality of user equipments; assigning a plurality of analogbeams to the plurality of precoded signals for each user equipment, inwhich each analog beam has a beam pattern defined by a beam width and abeam direction that is different for different analog beams; mappingprecoded signals assigned to different analog beams to differentresources, first precoded signals assigned to a first analog beam aremapped to a same time resource; and transmitting the precoded signals onthe corresponding resources to which the precoded signals are mapped, byusing at least one of the plurality of analog beams.
 2. The method ofclaim 1, wherein the transmitting comprises: converting the precodedsignals to a plurality of radio frequency (RF) signals; and transferringeach of the RF signals to at least one of antenna elements based on aswitching pattern determined based on corresponding analog beams.
 3. Themethod of claim 1, further comprising: multiplexing the plurality ofprecoded signals to a plurality of group signals, such that the precodedsignals assigned to a same analog beam are multiplexed into a groupsignal; prioritizing the plurality of group signals comprising theplurality of precoded signals by scheduling; determining whetherinterference between an analog beam corresponding to each group signaland a previously selected analog beam is less than a reference value inorder of priorities of the plurality of group signals; mapping theprecoded signals included in a group signal having interference lessthan the reference value to orthogonal frequency division multiplexing(OFDM) symbols to be transmitted; and repeating the determining and themapping until at least one of resources of assignable OFDM symbols areassigned and transmission for the plurality of analog beams isconsidered.
 4. The method of claim 1, wherein the plurality ofmodulation symbols are mapped to a plurality of layers before theprecoding.
 5. The method of claim 4, wherein the plurality of precodedsignals are generated based on at least one precoding matrix.
 6. Themethod of claim 1, wherein the mapping of the precoded signalscomprises: mapping the precoded signals for different user equipmentscorresponding to a same analog beam, to different frequency resources ofthe same time resource.
 7. The method of claim 1, wherein the mapping ofthe precoded signals comprises: mapping the precoded signals fordifferent user equipments corresponding to a same analog beam, todifferent time resources of a same frequency resource.
 8. The method ofclaim 1, wherein the mapping of the precoded signals comprises:identifying an analog beam having less interference among the pluralityof analog beams; and mapping at least one precoded signal assigned tothe identified analog beam to a same time-frequency resource.
 9. Themethod of claim 1, wherein a first analog beam that carries a firstprecoded signal for a first user equipment of the plurality of userequipments is determined as an analog beam selected for the first userequipment.
 10. The method of claim 1, wherein the precoded signalsassigned to at least one selected analog beam are mapped to a pluralityof orthogonal frequency division multiplexing (OFDM) signals and aretransmitted at the same time resource, and wherein the precoded signalsassigned to unselected analog beams are transmitted at a different timeresource than the precoded signals assigned to the at least one selectedanalog beam.
 11. An apparatus for transmitting signals in amulti-antenna system, the apparatus comprising: a controller configuredto: precode a plurality of modulation symbols to generate a plurality ofprecoded signals corresponding to a plurality of antenna ports for eachuser equipment among a plurality of user equipments, assign a pluralityof analog beams to the plurality of precoded signals for each userequipment, in which each analog beam has a beam pattern defined by abeam width and a beam direction that is different for different analogbeams, and map precoded signals assigned to different analog beams todifferent resources, wherein first precoded signals assigned to a firstanalog beam are mapped to a same time resource; and a transceiverconfigured to transmit the precoded signals on the correspondingresources to which the precoded signals are mapped by using at least oneof the plurality of analog beams.
 12. The apparatus of claim 11, whereinthe transceiver is further configured to: convert the precoded signalsto a plurality of radio frequency (RF) signals, and transfer each of theRF signals to at least one of a plurality of antenna elements based on aswitching pattern determined based on corresponding analog beams. 13.The apparatus of claim 11, wherein the controller is further configuredto: multiplex the plurality of precoded signals to a plurality of groupsignals, such that the precoded signals assigned to a same analog beamare multiplexed into a group signal; prioritize the plurality of groupsignals comprising the plurality of precoded signals by scheduling,determine whether interference between an analog beam corresponding toeach group signal and a previously selected analog beam is less than areference value, in order of priorities of the plurality of groupsignals, map the precoded signals included in a group signal havinginterference less than the reference value, to orthogonal frequencydivision multiplexing (OFDM) symbols to be transmitted, and repeat thedetermination and the mapping until at least one of resources of allassignable OFDM symbols are assigned and transmission for the pluralityof analog beams is considered.
 14. The apparatus of claim 11, whereinthe plurality of modulation symbols are mapped to a plurality of layersbefore precoding.
 15. The apparatus of claim 14, wherein the pluralityof precoded signals are generated based on at least one precodingmatrix.
 16. The apparatus of claim 11, wherein the controller is furtherconfigured to map the precoded signals for different user equipmentscorresponding to a same analog beam to different frequency resources ofthe same time resource.
 17. The apparatus of claim 11, wherein thecontroller is further configured to map the precoded signalscorresponding for different user equipments corresponding to a sameanalog beam to different time resources of a same frequency resource.18. The apparatus of claim 12, wherein the controller is furtherconfigured to: identify an analog beam having less interference amongthe plurality of analog beams, and map at least one precoded signalassigned to the identified analog beam to a same time-frequencyresource.
 19. The apparatus of claim 11, wherein a first analog beamthat carries a first precoded signal for a first user equipment of theplurality of user equipments is determined as an analog beam selectedfor the first user equipment.
 20. The apparatus of claim 11, wherein theprecoded signals assigned to at least one selected analog beam aremapped to a plurality of orthogonal frequency division multiplexing(OFDM) signals and are transmitted at the same time resource, andwherein the precoded signals assigned to unselected analog beams aretransmitted at a different time resource than the precoded signalsassigned to the at least one selected analog beam.